The present invention relates to meters for measuring usage of electricity in residential and commercial buildings. Such meters are typically referred to as xe2x80x9celectricity metersxe2x80x9d or xe2x80x9cwatt hour metersxe2x80x9d and generally include an electric motor in which speed is related to power used in the building. The motor includes an armature having a disk that is partially visible through the meter""s clear dome and that rotates at a speed proportional to instantaneous energy. The disk, in turn, drives gears of a numerical meter having dials that integrate instantaneous energy over time to indicate power, generally in watt hours. The difference between readings of the numerical meter at different times indicates electric power consumption during the intervening period.
Conventional electricity meters are read manually and, therefore, require that the electric utility send a field operator to periodically check every meter in the area it serves.
The present invention recognizes and addresses the foregoing disadvantages, and others, of prior art construction and methods.
Accordingly, it is an object of the present invention to provide an improved meter for measuring electric power consumption.
It is a further object of the present invention to provide an electricity meter that electronically derives data related to electricity usage.
Some of these objects are achieved by a meter for measuring electricity usage for a given load area. The meter includes a housing, a first light source and a second light source. Each light source is disposed in the housing and is configured to output light at a predetermined frequency. A first light receiver and a second light receiver are disposed in the housing so that a first light path is defined between the first light source and the second light source and so that a second light path is defined between the second light source and the second light receiver. Each light receiver is configured to receive the light from its respective light source and to output a signal responsively thereto at a frequency related to the predetermined frequency by a predetermined relationship. A rotatable member is disposed on the housing and is rotatable responsively to the electricity usage. The rotatable member defines a first portion and a second portion so that the first portion and the second portion alternatingly intercept each of the first light path and the second light path as the rotatable member rotates. The first portion transmits incident light from a light source to its respective light receiver. The second portion blocks incident light. One of the first portion and the second portion is defined on the rotatable member so that it intercepts only one of the first light path and the second light path at a time.
A filter circuit includes two bandpass filters. Each bandpass filter is in communication with a respective one of the first light receiver and the second light receiver and receives the output signal therefrom. The bandpass filter passes a frequency range that includes the related frequency so that the bandpass filter outputs a signal at the related frequency upon receipt of its light receiver""s output signal.
The filter circuit includes two acquisition circuits, each in communication with a respective one of the bandpass filters. Each acquisition circuit receives the output signal from its respective bandpass filter and is configured to output responsively thereto a signal having a magnitude based on the magnitude of the bandpass filter output signal.
The filter further includes two comparator circuits, each in communication with a respective one of the acquisition circuits. Each comparator circuit receives the output signal from its respective acquisition circuit and is configured to compare the acquisition circuit output signal with a threshold voltage and output a signal in one of two states depending on the comparison.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.